But, in the meantime, invention has been busy in other directions. Fire is so terrible a calamity, and its risks so great, that ingenuity has been taxed to the utmost to master it in every way; and not only to extinguish it, but to prevent it from occurring at all. Of a fire, indeed, it may be said that prevention is better than cure. What think you of muslin that will not flame, of ceilings that will pour forth water by themselves, of glass bottles that break and choke the fire? What think you of chemical fire-engines, some so small as to be easily carried on a man's back? or of curtains and screens and fabrics that stubbornly refuse to yield? All kinds of contrivances, in short, have been cleverly designed. Let us now see some in operation. Have you ever seen a fire choked in a minute? and how is it done? CHAPTER XIII. CHEMICAL FIRE-ENGINES. FIRE-PROOFING, OR MUSLIN THAT WILL NOT FLAME. Which structure will be first extinguished? Imagine yourself gazing at two wooden sheds, both quite filled with combustible materials, and drenched with petroleum and tar. These are to be fired, and then one is to be extinguished by water, and the other by an extinctor, or chemical fire-engine. "Ready!" At the word, the torch is applied, and the first shed bursts into flames. It soon blazes furiously. A man steps forward, armed with a hand-pump, such as is used by the Metropolitan Fire-Brigade, and turns a jet of water upon it. Hiss! squish! A cloud of steam rises as the water dashes upon the fire, and still the stream pours on. Now the fireman pauses to refill his pump with water, and then again the jet plays on the burning pile. The fire dims down to a dull red, the flames cease to shoot upward and outward, and after about five minutes the conflagration is extinguished. Bravo! A very smart piece of work! But now the second shed is lighted, and blazes fast. Another man hurries forward. He has a steel cylinder slung on his back, and in a second, without any pumping, he directs a jet of fluid upon the fire. The flames die down, the red gives place to blackness, and, in about half the time taken by the other method, the extinctor has completely quenched the fire. How is it done? [Illustration: CHEMICAL EXTINCTOR.] [Illustration: SECTION OF CHEMICAL FIRE-ENGINE.]